/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    TwoWayNumericSplit.java
 *    Copyright (C) 2001 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.classifiers.trees.adtree;

import weka.core.Instance;
import weka.core.Instances;
import weka.core.RevisionUtils;
import weka.core.Utils;

/**
 * Class representing a two-way split on a numeric attribute, of the form:
 * either 'is < some_value' or 'is >= some_value'.
 * 
 * @author Richard Kirkby (rkirkby@cs.waikato.ac.nz)
 * @version $Revision$
 */
public class TwoWayNumericSplit extends Splitter {

  /** for serialization */
  private static final long serialVersionUID = 449769177903158283L;

  /** The index of the attribute the split depends on */
  private final int attIndex;

  /** The attribute value that is compared against */
  private final double splitPoint;

  /** The children of this split */
  private final PredictionNode[] children;

  /**
   * Creates a new two-way numeric splitter.
   * 
   * @param _attIndex the index of the attribute this split depeneds on
   * @param _splitPoint the attribute value that the splitter splits on
   */
  public TwoWayNumericSplit(int _attIndex, double _splitPoint) {

    attIndex = _attIndex;
    splitPoint = _splitPoint;
    children = new PredictionNode[2];
  }

  /**
   * Gets the number of branches of the split.
   * 
   * @return the number of branches (always = 2)
   */
  @Override
  public int getNumOfBranches() {

    return 2;
  }

  /**
   * Gets the index of the branch that an instance applies to. Returns -1 if no
   * branches apply.
   * 
   * @param inst the instance
   * @return the branch index
   */
  @Override
  public int branchInstanceGoesDown(Instance inst) {

    if (inst.isMissing(attIndex)) {
      return -1;
    } else if (inst.value(attIndex) < splitPoint) {
      return 0;
    } else {
      return 1;
    }
  }

  /**
   * Gets the subset of instances that apply to a particluar branch of the
   * split. If the branch index is -1, the subset will consist of those
   * instances that don't apply to any branch.
   * 
   * @param branch the index of the branch
   * @param instances the instances from which to find the subset
   * @return the set of instances that apply
   */
  @Override
  public ReferenceInstances instancesDownBranch(int branch, Instances instances) {

    ReferenceInstances filteredInstances = new ReferenceInstances(instances, 1);
    if (branch == -1) {
      for (Instance instance : instances) {
        Instance inst = instance;
        if (inst.isMissing(attIndex)) {
          filteredInstances.addReference(inst);
        }
      }
    } else if (branch == 0) {
      for (Instance instance : instances) {
        Instance inst = instance;
        if (!inst.isMissing(attIndex) && inst.value(attIndex) < splitPoint) {
          filteredInstances.addReference(inst);
        }
      }
    } else {
      for (Instance instance : instances) {
        Instance inst = instance;
        if (!inst.isMissing(attIndex) && inst.value(attIndex) >= splitPoint) {
          filteredInstances.addReference(inst);
        }
      }
    }
    return filteredInstances;
  }

  /**
   * Gets the string describing the attributes the split depends on. i.e. the
   * left hand side of the description of the split.
   * 
   * @param dataset the dataset that the split is based on
   * @return a string describing the attributes
   */
  @Override
  public String attributeString(Instances dataset) {

    return dataset.attribute(attIndex).name();
  }

  /**
   * Gets the string describing the comparision the split depends on for a
   * particular branch. i.e. the right hand side of the description of the
   * split.
   * 
   * @param branchNum the branch of the split
   * @param dataset the dataset that the split is based on
   * @return a string describing the comparison
   */
  @Override
  public String comparisonString(int branchNum, Instances dataset) {

    return ((branchNum == 0 ? "< " : ">= ") + Utils.doubleToString(splitPoint,
      3));
  }

  /**
   * Tests whether two splitters are equivalent.
   * 
   * @param compare the splitter to compare with
   * @return whether or not they match
   */
  @Override
  public boolean equalTo(Splitter compare) {

    if (compare instanceof TwoWayNumericSplit) { // test object type
      TwoWayNumericSplit compareSame = (TwoWayNumericSplit) compare;
      return (attIndex == compareSame.attIndex && splitPoint == compareSame.splitPoint);
    } else {
      return false;
    }
  }

  /**
   * Sets the child for a branch of the split.
   * 
   * @param branchNum the branch to set the child for
   * @param childPredictor the new child
   */
  @Override
  public void setChildForBranch(int branchNum, PredictionNode childPredictor) {

    children[branchNum] = childPredictor;
  }

  /**
   * Gets the child for a branch of the split.
   * 
   * @param branchNum the branch to get the child for
   * @return the child
   */
  @Override
  public PredictionNode getChildForBranch(int branchNum) {

    return children[branchNum];
  }

  /**
   * Clones this node. Performs a deep copy, recursing through the tree.
   * 
   * @return a clone
   */
  @Override
  public Object clone() {

    TwoWayNumericSplit clone = new TwoWayNumericSplit(attIndex, splitPoint);
    clone.orderAdded = orderAdded;
    if (children[0] != null) {
      clone.setChildForBranch(0, (PredictionNode) children[0].clone());
    }
    if (children[1] != null) {
      clone.setChildForBranch(1, (PredictionNode) children[1].clone());
    }
    return clone;
  }

  /**
   * Returns the revision string.
   * 
   * @return the revision
   */
  @Override
  public String getRevision() {
    return RevisionUtils.extract("$Revision$");
  }
}
